1. Field of the invention
This invention relates to a laser beam machine for performing laser beam machining according to a machining program, and more particularly to a laser beam machine which executes laser beam machining under the optimum machining conditions.
2. Description of the Related Art
Conventionally, when a laser beam machine cuts a workpiece by collecting the laser beam and irradiating same on the workpiece, the positional relationship between a surface of the workpiece and a converging point of the laser beam has much influence on the performance of the laser beam machine. The optimum position of the converging point of the laser beam relative to the surface of the workpiece varies with the kind of material of the workpiece. Therefore, in cutting the workpiece as well, the converging point of the laser beam is set to the optimum position dependent on the material of the workpiece.
The position of the converging point of the laser beam is fixed for the same kind of material.
However, recent research revealed the fact that even in cutting off the same kind of material, the optimum position of the converging point of the laser beam varies between piercing carried out at the start of the machining and cutting carried out thereafter.
However, conventional laser beam machines are adapted to cut off workpieces by setting the position of the converging point of the laser beam to the optimum position for cutting for the purpose of enhancing cutting accuracy, which requires a time period unnecessarily long for piercing.